Symptomatic and asymptomatic malaria prevalence and its determinant factors in pastoral communities of Waghemira Zone, Northeast Ethiopia: A community‐based cross‐sectional study

Abstract Background and Aims Malaria elimination programs have also encountered numerous challenges, such as widespread asymptomatic carriers in endemic areas, which should be taken into account in malaria‐control programs for effective transmission interruption. The purpose of this research was to determine the prevalence of symptomatic and asymptomatic malaria infections and associated factors, in pastoral communities. Methods A community‐based cross‐sectional study was conducted among selected districts in the Waghemra Zone, Northeast Ethiopia, from September to December 2022. A structured questionnaire was employed to collect sociodemographic data and associated risk factors. Plasmodium species were detected using light microscopy and a rapid diagnostic test. Data entry and analysis were carried out using SPSS version 26 software. The association between dependent and independent variables was explored by using multivariable logistic regression analyses. A statistically significant association was declared at a p‐value of <0.05. Results The overall prevalence of malaria was 21.2% (134/633), with the predominant Plasmodium falciparum infections accounting for 67.8% (87/134). Among asymptomatic participants, 7.5% (34/451) and 10.2% (46/451) were diagnosed by rapid diagnostic test and light microscopy, respectively. On the other hand, the prevalence of symptomatic malaria was 44.5% (81/182) and 48.4% (88/182) as diagnosed by rapid diagnostic test and light microscopy, respectively. The presence of stagnant water near the houses, the utilization of insecticide‐treated mosquito nets, the number of insecticide‐treated mosquito nets, and outdoor stays at night were all positively linked with the prevalence of malaria. Conclusions The overall prevalence estimate for symptomatic and asymptomatic malaria was high. Malaria is still a public health problem in the study area. Malaria infection was associated with the presence of stagnant water near the houses, the utilization of insecticide‐treated mosquito nets, the number of insecticide‐treated mosquito nets, and outdoor stays at night. Improved access to all malaria interventions is needed to interrupt the transmission at the community level.

that has had great success. 4 Malaria incidence has decreased from 5.2 million in 2015 to less than 1 million in 2019. Malaria deaths fell from 3.6 to 0.3 per 100,000 people at risk. 5,6 However, Ethiopia still accounts for 1.7% of all malaria cases worldwide. In 2021, there were 2,783,816 cases and 8041 deaths. 7 Malaria primarily affects the community during the planting and harvesting seasons, when agricultural labor is most needed. Healthcare institutions are overburdened with patients during epidemics, and many resources are diverted to deal with the situation. This places a major financial burden on poverty alleviation. 8,9 Ethiopia has launched a malaria elimination program with the goal of eliminating the disease by 2030. To achieve this objective, the government is now focusing on three key malaria prevention strategies: early diagnosis and rapid treatment; vector control methods such as indoor residual spraying (IRS) and insecticide-treated bed nets (ITNs); and surveillance. 4,10 Malaria control and elimination are becoming increasingly difficult in many nations, including Ethiopia. The prevalence of asymptomatic carriers, the evolution of insecticide-resistant vectors and drug-resistant Plasmodium species, and a lack of long-term and stable financing are among the challenges. 7 Asymptomatic malaria infections are almost certainly a significant parasite reservoir, enabling parasite transmission to continue. 11,12 This is due to the fact that, asymptomatic carrier parasites are more infectious to the Anopheles mosquito and serve as a major source of gametocytes for local mosquito vectors, which helps to maintain malaria spread. 13,14 These factors hampered the government's attempts to control and eliminate malaria.
In high-endemic areas, asymptomatic malaria infection is more prevalent. 15 Active surveillance is frequently used to detect asymptomatic malaria infections. Furthermore, a small proportion of infected individuals is sufficient to restart malaria transmission in regions where malaria transmission is seasonal and low. 16,17 In addition to other preventive and control measures, the national malaria elimination program should target the identification of both symptomatic and asymptomatic malaria in communities and treat them with appropriate anti-malarial medications. 18,19 This is especially true in the Waghemra Zone, where both symptomatic and asymptomatic malaria are prevalent.
Despite the fact that some research on asymptomatic or symptomatic both types of malaria are conducted in various locations of Ethiopia, they often focus on health institution-based studies and pregnant women. As a result, understanding the present prevalence of symptomatic and asymptomatic malaria, as well as the risk factors linked with it, in communities is critical for scaling up intervention programs. In the study area, there has been no research on the prevalence of symptomatic and asymptomatic malaria. As a result, the purpose of this study was to determine the prevalence of symptomatic and asymptomatic malaria, as well as associated factors, among pastoral communities in the Waghemra Zone.
Accounting for a 10% nonresponse rate and implementing design effect of 1.5, the final sample size was 633.

| Sampling techniques and procedure
A stratified sampling method was used to select the representative sample size. The total households for each village were available at their nearest health post, which is stored as a family card folder, to determine the proportional sample size for each selected kebele.
Based on this, the total sample size was proportionally allocated as 146, 104, 127, 81, 114, and 61 households to Tsitsika, Netsawork, Silazge, Meharit, Saka, and Debre-brihan kebeles, respectively. Each household was selected using a systematic random sampling technique. Finally, one of the selected household members was chosen at random using a lottery method.

| Inclusion and exclusion criteria
Individuals with and without clinical malaria symptoms who are permanent residents of the districts were included in the study. On the other hand, individuals who had taken antimalarial medications in the 4 weeks before the research period were excluded.

| Sociodemographic and other factors
A structured questionnaire was used to collect information from each participant, including associated factors such as background characteristics, behavioral, environmental, and other factors relevant to malaria infection. Selected adult participants were interviewed directly; for children, parents were involved in the interview process.
After the selection of the study participants in the households, body temperature and other clinical manifestations were examined by senior BSc nurses to identify symptomatic and asymptomatic individuals.

| Blood sample collection, transportation, and examination
In addition to sociodemographic and other variables, blood samples were taken aseptically from each subject via a finger prick with a disposable sterile lancet. Rapid diagnostic test (RDT) and blood films were used to screen the samples for malaria parasites.

RDT (CareStartTM malaria Pf/Pv [HRP2/pLDH]) Ag combo test
After the bag was opened, the capillary sample was wiped onto the sample pad of the test kit for instant use. After about two drops of buffer were placed in the buffer pad, the result was read after 20 min. 20

Blood film examinations
For each participant, thin and thick blood films were produced on the same slide and labeled with a unique code for the microscopic study of Plasmodium spp. The thin blood smear was fixed after drying by delicately dripping methanol with a Pasteur pipette. The methanolfixed thin smears were permitted to dry completely in the air by placing the slides on a level surface (about 2 min). The blood smears were transported to nearby health facilities in a slide box for giemsa staining. At least 100 high-power fields (100 objectives) were assessed before reporting a negative result. 21

| Quality control
The questionnaire was pretested, and the data collectors received training. The expiration dates of the RDT kits were examined. The manufacturer's instructions were strictly followed for the RDTs.
Positive and negative blood films were run to ensure the quality and integrity of the giemsa staining. Two experienced laboratory technologists individually examined the microscopic slides. Hundred microscopic fields of the thick smear were examined before concluding as negative. The discrepancy between the first and second readings was settled by a third senior laboratory technologist.
Blood smear microscopy readers was blinded to the results of RDTs.
Houses that were absent during the first visit were revisited again in the following day to ensure maximum involvement. All test methods and results were interpreted in accordance with standard operating procedures.

| Data analysis and interpretation
Following data collection, SPSS version 26 was used to enter and analyze the data. Descriptive statistics were used to assess the prevalence rate and determining factors. To assess an association of factors with malaria infection, bivariable and multivariable logistic regression models were utilized. In the bivariable analysis, variables having a p-value of less than or equal to 0.25 were included in the multivariable logistic regression analysis.
The 95% CI was used to determine the odds ratio (OR), and a p-value of less than 0.05 was considered statistically significant.
Finally, the study's findings were presented in text and tables as appropriate.

| Sociodemographic characteristics of study participants
In this study a total of 633 asymptomatic and symptomatic patients, with a 100% response rate were included. In terms of age category, 43.4% (275/633) of participants were between the ages of 15 and 45. Of the overall study participants, 48.5% (307/633) were farmers, and 79.3% (502/633) had a family size of 4−6 people (Table 1).  (Table 2).  (Table 3).

| Asymptomatic and symptomatic malaria
Among 115 asymptomatic and symptomatic malaria-infected individuals detected using RDT in the survey, Plasmodium falciparum, Plasmodium vivax, and mixed accounted for 67.8%, 29.6%, and 2.6%, respectively. P. falciparum, P. vivax, and mixed parasites were found in 65.0%, 31.3%, and 3.7% of 134 microscopically confirmed asymptomatic and symptomatic malaria cases, respectively. All RDT-positive cases were also positive using microscopy (Table 4).   25 and Bagamoyo district, Tanzania (57.5%). 28 This difference could be attributed to geographical differences relative to the current study area, as the aforementioned area is extremely malarial and the population is constantly exposed to malaria, which could contribute to the development of immunity, resulting in asymptomatic malaria. 36 Furthermore, the diagnostic method we used differed from those used in a Tanzanian study that used a molecular technique and in Douala, Cameroon, LED fluorescence microscopy was used for malaria detection, which is very sensitive;

and Maygaba
Town, Northwest Ethiopia (4.7%). 41 The differences might be due to inadequate environmental and vector control interventions in affected areas. The national malaria prevention and control strategies recommend the application of the IRS at least once a year with 100% coverage and at least one ITN per two people in malaria high-risk areas. 42 Despite this fact, IRS was not applied before the study period, and early replacement of ITNs was not done. Households that had been using the ITNs for purposes other than their intended purpose were also observed. This could be due to poor monitoring of the communities after distributing the ITNs.
This study showed that the prevalence of symptomatic malaria in pastoral communities of Waghemra Zone was 48.4% (95% CI = 44.2−53.0). The prevalence of this study was lower than a study done in Ibadan, Nigeria (55.0%). 43 This disparity could be attributed to differences in study design and setting; for example, the study in Ibadan, Nigeria, was done in health facilities, which may have overestimated the prevalence compared to a community-based study. In contrary to this, the prevalence of symptomatic malaria in this study was higher than reported in Ziquala district, Northeast Ethiopia (24.6%), 44 Lake Tana and its surrounding areas, Northwest Ethiopia 24.7%, 45 the Mount Cameroon area (41.7%), 46 the Pakro subdistrict of Ghana 32.9%, 47 and Dzanga Sangha Region, Central African Republic (35.2%) 48 and Malawi (19.0%). 49 This variation might be attributed to the different data collection periods, settings, laboratory method, and laboratory personnel skills.
In general, the prevalence of malaria differed between symptomatic and asymptomatic individuals in this study. This disparity could be attributed to the fact that we used various sample sizes and that the diagnosis was performed using low-sensitivity techniques, particularly for the diagnosis of asymptomatic malaria. 37 Asymptomatic malaria patients have acquired partial immunity, which clears the parasite and results in a low parasite density compared to symptomatic patients. As a result, poor sensitivity techniques such as microscopy and RDT may miss detecting asymptomatic malaria. 37,50 This study revealed that the predominant Plasmodium species detected was P. falciparum (65.0%), followed by P. districts of the Amhara region of Ethiopia. 44,58,59 This could be explained by the exophagic-exophilic biting behaviors of mosquitoes. 60 This could also be attributed to the hot weather, as people prefer to sleep outside to get fresh air and cool off, and this could make it difficult to use ITNs while sleeping outside.

| Limitation of the study
This study maintained its strength by using larger samples and sampling approaches to reduce selection bias and assure internal and external validity. Confounding factors were also eliminated with the help of binary logistic regression analysis. In this study, like any crosssectional study, it is difficult to establish a causal association.
Furthermore, due to a shortage of resources, this study was unable to apply the molecular tool PCR for detecting malaria to support RDT and microscopic investigation.

| CONCLUSION AND RECOMMENDATIONS
In this study, the overall prevalence estimate of symptomatic and asymptomatic malaria was high. Among Plasmodium species, P.
falciparum was found to be the most prevalent in the study area.

ACKNOWLEDGMENTS
The authors thank the study participants, data collectors, Waghemra Zone Health Office. The authors would like to also thank district health offices, kebele leaders, health extension workers, health facility administrative, and medical laboratory staffs for their support and unreserved cooperation in making this study to be a fruitful work.

CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT
All relevant data are included in the published article.

ETHICS STATEMENT
Ethical clearance was obtained from the ethical review committee of